1. Field of the Invention
My invention relates to electroplating apparatus and, in particular, to such apparatus especially well adapted for the continuous manufacture of metal foil or printed electronic circuit patterns.
2. Description of the Prior Art
In K. Yamashita et al. U.S. patent application Ser. No. 722,479, filed on Sept. 13, 1976 under the title, "Process for the Fabrication of Printed Circuits", now patent No. 4,053,370, and assigned to the instant assignee, there is disclosed an electroplating apparatus wherein an endless strip of basis metal extends over a pair of rolls one of which is made cathodic in an acid copper bath. Copper is electrodeposited on the basis metal as the latter, traveling over the cathode roll, is held opposite to insoluble anodes in the bath while the electrolyte solution is made to flow turbulently therebetween to realize a high deposition rate. It has later been discovered, however, that this "rotary" electroplating apparatus, on which the mentioned patent is based, has the following problems.
In the "rotary" electroplating apparatus of the above type, the diameter of the cathode roll is determined by the thickness and other properties of the endless strip of basis metal traveling thereover, in accordance with the equation: EQU R = (E .times. t/2(1 - .mu..sup.2)S)
where R is the diameter of the cathode roll, E is the elastic modulus of the basis metal, t is the thickness of the basis metal, .mu. is the Poisson ratio of the basis metal, and S is the fatigue limit of the basis metal. Since the endless strip of basis metal becomes flattened as same travels past the cathode roll of the above defined diameter, the copper or other metal which has been electrodeposited on the curved surface of the basis metal traveling over the cathode roll is subjected, when the basis metal is subsequently flattened, to a stress such that the electrodeposit tends to separate prematurely from the basis metal.
It is also a disadvantage of the prior art apparatus that the thickness of basis metal for use is limited, in relation to the diameter of the cathode roll, in accordance with the above formula. Furthermore, in the "rotary" electroplating apparatus, it is difficult to effectively and durably seal the electroplating tank against the overflow of the electrolyte solution which is caused as aforesaid to flow turbulently between the rotary cathode and the stationary anodes.